Thermodynamics of biochemical reactions


Alberty, Robert A.; John Wiley & Sons, Inc., Hoboken, New Jersey, 2003, 408 pp., ISBN 0-471-22851-6, $69.95

The stated purpose of this book is to apply the principles of chemical thermodynamics to the enzyme-catalyzed reactions that comprise metabolism. The author, a distinguished physical chemist who is a Professor Emeritus at MIT, states that the book is designed for students who have taken a first course in physical chemistry; obviously, then, familiarity with principles of biochemistry is essential, as well.

It is a truism that living systems obey the laws of thermodynamics and, hence, that the energetics of cells can be described by the equations of chemical thermodynamics. The author points out several significant ways in which biochemical thermodynamics requires new concepts and equations. For example, biochemists usually think of ATP as a single molecular species, but in fact ATP comprises several different ionic species at physiological pH. Biochemical reactants are often ions, whose activities depend strongly on the ionic strength of the medium. Moreover, ions such as Mg2+ exist in both free and bound form, either to nucleotides or to proteins, or both. Biochemical reactions often interconvert chemical energy with light, electrical, or mechanical energy. Metabolism consists of complex linked networks of reactions, rather than the single reactions most easily studied by classical thermodynamics. Alberty deals with these and other complexities in a rigorous, but generally clear, fashion.

Alberty states, as a major theme of the book, the use of Legendre transforms to make applications of thermodynamics easier for users, by introducing intensive variables as independent variables. This was done originally by J. Willard Gibbs, when he related the internal energy of a system, U, to enthalpy, H, and Gibbs free energy, G, in terms of the variables temperature and pressure. Biochemical thermodynamics does likewise when it creates new parameters, such as G′, the free energy at a fixed pH. Alberty goes on to use additional Legendre transforms, for instance, when considering reactions involving coenzymes, in which it is assumed that coenzyme concentrations remain constant during a reaction.

This book is a useful learning device that could be used either as a textbook for a graduate-level course in biochemical thermodynamics, or for individual study by those whose need to understand biochemical energetics extends well beyond what can be presented in elementary physical chemistry or biochemistry textbooks. Eleven chapters of text make up about half of the book, and the remaining half consists of problems relevant to each chapter, with solutions worked out and presented in detail, with the help of the Mathematica program ( Four pages of references are categorized by year, starting with 1873 and a reference to The Scientific Papers of J. Willard Gibbs, Vol. I. Thermodynamics. However, to emphasize that this is a still-evolving field, about two thirds of the references are dated 1990 or later.

This reviewer has a long relationship with Professor Alberty, although I have never met the gentleman. In 1957, as a college senior, I used Physical Chemistry, by Daniels and Alberty, as the text for my first physical chemistry course, and we also used the companion text, Experimental Physical Chemistry, as our lab manual. More recently, as biochemistry textbook authors, my coauthor, Ken van Holde, and I have regularly received long letters from Professor Alberty, gently but firmly making us aware of oversimplifications or errors in our own presentations. I suspect that we are not the only biochemistry textbook authors who have heard from Professor Alberty. Textbook authors, including the distinguished co-editors of Biochemistry and Molecular Biology Education, must tread a fine line between clarity and accuracy on the one hand, and liveliness of writing style and conciseness on the other. Inevitably, oversimplifications occur. Through the writing of his new book, Professor Alberty has performed a great service to future textbook authors and to their readers, as well as to the biochemical community in general.